Rotary printing machine



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A-TraRNEY Jan. 8, 1963 F. WOLFF ROTARY PRINTING MACHINE 9 Sheets-Sheet 5 Filed July 21, 1960 Jan. 8, 1963 Filed July 21, 1960 F. WOLFF ROTARY PRINTING MACHINE 9 Sheets-Sheet 6 53 50 I Mum/ran frlw/rz WaLFF mr m ay w Jan. 8,' 1963 F OLFF ROTARY PRINTING MACHINE 9 Sheets-Sheet 7 Filed July 21, 1960 INVENTOR FR/TZ WOL FF Jan. 8, 1963 woL 3,072,050

ROTARY PRINTING MACHINE Filed July 21, 1960 9 Sheets-Sheet 8 Arrorwsy United States Patent ()ffice 0,072,050 Patented Jan. 8, 1963 3,tl72,050 RUTARY PRINTiNG MACHINE Fritz Wolff, Weichselstrasse 5, Numberg, Germany Filed July 21, 1960, Ser. No. 44,3d4 Claims priority, application Germany July 27, 1%9 4 Claims. (Cl. 1911'77) The present invention relates to rotary presses or printing machines, and more particularly to a novel arrangement of cylinders and of associated apparatus in such a press.

The printing processes performed on rotary presses may be generally classified as relief printing including letterpress printing, intaglio printing, and offset printing. Each of these processes, as conventionally performed, requires a different arrangement of cylinders in a different machine. A rotary press of the designs heretofore employed is capable of performing only one of the processes cited.

Relief printing is resorted to almost exclusively in newspaper work where it is necessary to replace portions of the printing form on short notice when late news is received. The printing plates which are cast from type metal and clamped to the cylindrical face of a form cylinder permit such replacement of portions of the form within a very short span of time. News received shortly before printing time can thus be included in the printed text.

Where editions are limited in volume, it is much more economical to prepare offset printing plates of zinc, aluminum, trimetal and the like than stereotypes. Conventional offset plates, however, do not permit quick changes of individual sections with the rapidity that is essential in newspaper work.

It is an object of my invention to provide a newspaper printing machine having a plurality of printing units on which portions of a newspaper may be alternatively printed by relief printing or by offset methods so that an entire edition may be printed by one of the two methods, or the bulk of the paper may be offset, whereas the late news section is prepared by relief printing.

Another object of the invention is to provide a press which enables a relatively small printing shop to accept both offset and relief printing work for rotary presses without the need of installing separate machinery for each type of operation.

Generally, it is the object of the invention to provide a printing machine or press which is universally adapted to the several printing processes enumerated with only very minor adjustments.

With these and other objects in view, the printing press of my invention is equipped with a first and a second pair of cylinders, each pair consisting of an outer and an inner cylinder mounted on the machine frame. The cylinders of each pair have parallel axes and are in peripheral abutting engagement along an axial line of their respective cylindrical faces. To permit changeover between offset and relief printing operations, I provide means for moving at least the inner cylinder of one of the pairs, or both cylinders of at least one of the pairs, toward and away from a position in which the axes of the two inner cylinders are parallel and the two inner cylinders are in peripheral abutting engagement.

Printing plates or other facings can be mounted on the cylindrical surfaces of the outer cylinders, and may be either of the stereotype or other relief printing plate type, or of the offset type. To secure offset plates to an outer cylinder, I equip the cylinder with tensioning means. Packing is interposed between the cylinder surface and the offset plate where required.

The inner cylinders are equipped to receive either offset blankets of rubber or rubber-like material, or relief impression facings of glass fibers, cork and the like as is usual on impression cylinders in relief printing.

To move at least one of the inner cylinders toward a position of contact of the inner cylinders, that is, a position in which all four cylinders are in sequential peripheral abutting engagement as is required for perfecting offset printing, and toward a position in which the inner cylinders are spaced from each other and the two pairs of cylinders are adapted for perfecting relief printing, 1 may employ several arrangements.

According to one feature of my invention, the shaft of at least one of the inner cylinders is journaled in the bore of an eccentric bearing bushing which is rotatably mounted in the machine frame. Adjustment of the bushing position permits shifting of the axis of the inner cylinder in a transverse direction into and out of engagement with the other cylinder.

According to another alternate feature of my invention, one of the cylinder pairs is mounted on a movable portion of the machine frame which may be moved toward and away from a position of inner cylinder contact.

It is furthermore contemplated to mount one of the inner cylinders on brackets hinged to the machine frame for pivoting movement about the axis of the corresponding outer cylinder to achieve the desired adjustability of inner cylinder relationship.

To permit use of a the machine of the invention for offset printing, I provide a damping system arranged to transfer moisture to at least one of the outer cylinders.

For greatest versatility, I prefer to assemble at least two printing units, each having two pairs of printing cylinders to form a single machine.

Other features and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of preferred embodiments thereof when considered in connection with the acompanying drawings in which like reference numerals designate like or corresponding parts throughout the several figures thereof, and wherein:

FIG. 1 schematically illustrates the relative positions of the cylinders, and the path of the paper web in the press of the invention when set for offset printing, the view being taken in side elevation;

FIG. 2 shows the device of FIG. 1 when set for perfecting relief printing;

FIG. 3 is a side-elevational view of a printing press with parts of the structure broken away to show the cylinders arranged for relief printing in the manner illustrated by FIG. 1;

4 shows the press of FIG. 3 when set for offset printing;

FIG. 5 is a side elevational view of a press embodying two printing units of the invention, the view being taken in side elevation with portions of the structure removed to reveal the cylinder arrangements;

FIG. 6 is a side-elevational View, partly in section, 0 the inner cylinders and of associated elements for controlling their relative movement in a first preferred embodiment of the invention;

FIG. 7 is a fragmentary sectional plan view of the apparatus of FIG. 6;

FlG. 8 is a fragmentary sectional front elevation of the apparatus of FIG. 6;

FIG. 9 is a side-elevational view, partly in section, of the cylinder arrangement and associated elements in a second preferred embodiment of the invention;

FIG. 10 shows the apparatus of FIG. 9 in sectional plan view;

PEG. 11 illustrates a third embodiment of the invention in side elevational, partially sectional view;

FIG. 12 shows the apparatus of FIG. 11 in section on the line XII-XII.

FIG. 13 is a fragmentary sectional view of the apparaa 3 tus of FIG. 11, the section being taken on the line XIIIXIII.

FIG. 14 illustrates an axial section through one of the cylinders of FIGS. 1 to 13.

FIG. 15 shows a radial section taken on the line XVXV of FIG. 14;

FIG. 16 shows a modification of the apparatus of FIG. 14;

FIG. 17 shows yet another modification of the apparatus of FIG. 14;

FIG. 18 illustrates a third modification of the apparatus of FIG. 14;

FIG. 19 is a radially sectional view of the device of FIG. 18, the section being taken on the line XIX-XIX;

FIG. 20 shows a detail of the device of FIG. 19 on a greatly enlarged scale;

FIG. 21 is a side elevational detail view, partly in section, of another cylinder of the machines of FIGS. 1 to 13; and

FIG. 22 shows a portion of a damping system for a press according to the invention in plan view, partly in section.

Referring now to the drawing, and initially to FIG. 1, there are shown two pairs of cylinders Ia, 2a and 1b, 2b arranged for offset printing on a web of paper 3 which travels in the direction of the arrows. The four cylinders are in sequential peripheral abutting engagement along the axial lines 4, 5 and 6, the paper web 3 being inserted between the two inner cylinders 2a and 212. For offset printing, the inner cylinders are equipped wtih offset blankets whereas the outer cylinders la and 1b have printing plates mounted on their cylindrical faces.

As shown in FIG. 2, the two pairs of cylinders are arranged for perfecting relief printing. The two inner cylinders 2a and 2b, While still in abutting engagement With the corresponding outer cylinders along the lines 5 and 6, have been displaced relative to each other so as to form a gap 8. The paper web 7 is trained over the cylinders in an S-shaped path. The web '7 is wrapped about major portions of the inner cylinder surfaces and makes only tangential contact with the outer cylinders at 5 and 6 respectively. The outer cylinders in this arrangement carry printing plates for printing on the two sides of the web 7 in a single run through the press whereas the inner cylinders are provided with a facing of glass fibers, cork, and the like to act as impression cylinders in the usual manner.

FIGS. 3 and 4 illustrate the cylinder arrangements of FIGS. 1 and 2 respectively as mounted in otherwise conventional rotary presses equipped with a damping and inking system 9a and 9b for each pair of cylinders. Each system has a fountain for damping liquid and three rollers for transferring the liquid from the fountain to one outer cylinder, and another fountain and a multiplicity of rollers for-transferring ink to. the other outer cylinder. The damping systems are not required and are inactivated for relief printing as will be disclosed more fully as the description of specific embodiments of the invention proceeds. The paper web 7 is unwound from a roll of stock 10 and is passed to a folding and cutting device 11 after printing. Since feed systems for rotary presses are well known and are not part of this invention, a more detailed description of such auxiliary equipment is omitted.

In the press of FIG. 3, the inner cylinders 2a and 2b are separated by the gap 8, and the press is arranged for perfecting relief printing, that is, printing on the two sides of the paper web 7 in a single press run with stereotype printing plates mounted on the outer cylinders 1a and 1b. While reference is being made to stereotypes in describing preferred embodiments of relief printing by this invention, it will be appreciated that the invention is not limited to rotary printing plates produced by any specific method, and that its adaptability to many types of printing plates and printing processes is an important feature.

As shown in FIG. 4, the inner cylinders 2a and 2b are in abutting engagement for offset printing in the manner described above in connection with FIG. 1.

FIG. 5 is a side-elevational view of a rotary printing press equipped with two printing units of the invention, each equipped with two pairs of cylinders. The unit 12 has its cylinders set for relief printing on a paper web 7 whereas the unit 13 is arranged for offset printing on a second web 3, the printed sheets produced by both units being combined by folding in the cutting and folding device 11 as customary in newspaper work.

While the apparatus of FIG. 5 is arranged for producing two sheets which are offset and relief printed respectively, it will be understood by those skilled in the printing art that a single web of paper may be sequentially passed through both units to produce two superimposed impressions as is customary in multi-color work, that each unit may be employed to print one side only of a single web by different printing processes, that both units may be arranged to perform the same printing process on one or two different webs, and the like. The many variations and permutations of arrangements to which the press of FIG. 5 lends itself are an important advantage of this invention, and the versatility of a single machine capable of performing different printing operations simultaneously or sequentially, makes it particularly suitable for the relatively small printing shop.

While two printing units 12 and 13 have been illustrated in FIG. 5, the apparatus shown is intended to be merely illustrative of a multi-unit press which may be either initially built with any desired number of printing units, or which may be equipped with additional units as the need arises.

A first embodiment of means for moving the cylinders of a printing unit into and out of peripheral abutting engagement of the inner cylinders 2a and 2b, is illustrated in FIG. 6 which shows the cylinders and associated elements in side elevation, partly in section. FIGS. 7 and 8 show at least portions of the same device in plan view and front elevation respectively.

An outer eccentric bushing 15 is rotatably mounted in the machine frame 14 at each end of the cylinders 2a and 2b. The eccentric bore of the bushing 15 rotatably encloses an inner bushing 16 in the eccentric bore of which the shaft 17 of an inner cylinder 2a or 2b is journaled in an anti-friction bearing 34. The angular position of the outer bushing 15 is adjusted and secured by an integral worm wheel 18 which cooperates with a worm 19 of a spindle 20. The spindle 20 is rotatably mounted on the frame 14 in axially fixed position. Each spindle 20 carries a bevel gear 21 which meshes with a bevel gear 22 on one of two shafts 23 coordinated with a respective inner cylinder and equipped with a handwheel 24. Rotation of a handwheel 24 causes identical rotation of the two outer eccentric bushings 15 of an inner cylinder in such a manner that the inner cylinder moves radially toward and away from the other inner cylinder. In order to keep the angular displacement of each cylinder relatively small, I prefer to make the positions of both inner cylinders adjustable, but it will be understood that shifting a single inner cylinder may achieve some of the advantages of the invention.

The inner eccentric bushing 16 is arranged within the outer bushing 15 in such a manner that angular displacement of the bushing 16 will radially move the inner cylinder 2a, 2b toward and away from the corresponding outer cylinder 1a, 1b to vary contact pressure between the members of each cylinder pair as desired.

The control mechanism for angularly shifting the inner bushings 16 includes a radial arm 25 integral with the bushing 16, a connecting link 26 hingedly attached to the arm 25, and a double bell crank lever 27 pivotally mounted on the machine frame. Two arms of the lever 27 are respectively connected to two links 26 on the same side of two inner cylinders 2a, 211. A third arm of the lever 27 is actuated by a rod 28 which is part of a linkage connecting the two levers 27 on opposite sides of the printing unit to a single adjustment handle for simultaneous movement of the four inner bushings 16 of the printing units.

As best seen from FIG. 6, the axis 29 of the bushing is spaced from the axis of the cylinder and of its shaft 17 which is at 36 when the cylinder is in the posiiton 2a, 212, shown in solid lines. Rotation of the bushing 15 by the control apparatus described causes the axis of rotation of the cylinder to shift from 30 to 31, the cylinder simultaneously shifting from the position 2:: or 2b which is necessary for offset printing, to the position 32a, 32b indicated by broken lines, in which the cylinders no longer make contact at 4 but are spaced from each other by the cap 8. The machine is now set for relief printing. The cylinders 2a, 2b remain in peripheral abutting engagement with the corresponding outer cylinders 1a, 1b during the shift. The corresponding drive gears 33 of which only one is shown in FIG. 8 remain meshed.

Different means for moving the cylinders of a printing unit of the invention toward and away from a position of abutting engagement of the inner cylinders are illustrated in FIGS. 9 and 10 in side elevational and sectional plan view respectively. Swinging arms 35 and 36 are mounted on the frame 14, of the presses on bushings 37 which enclose the bearings at the two ends of the outer cylinder 1a. The arms 35 and 36 are rotatable on the bushings 37 and thus pivotable about the outer cylinder axis. The arms 35 and 36 carry between them the inner cylinder 1b which is thereby angularly displaceable about the axis of the corresponding outer cylinder without change in the radial spacing of the cylinder pair.

The angular position of the cylinder 2a relative to its outer cylinder in is controlled by a handwheel 33 which is mounted on the frame 14' by means of a pin 39 carrying two bevel gears 40. The latter mesh with respective bevel gears41 which actuate rotation of screw spindles 42, in blocks 43. The blocks are tiltably secured to the frame 14. The threads of the spindles 42 engage mating threaded sleeves 4 4 which are hinged to the arms 35 and 36 respectively by means of pivot pins 45. Rotation of the handwheel 33 thus shifts the cylinder Zn from the solid line position for offset printing to the relief printing position indicated by broken lines 46. Since the center of arcuate radial movement of the cylinder 2a coincides with the axis of the cylinder in, there is less need for adjusting the relaitve position of cylinders in and 2a, and the angular displacement of the inner cylinder may be selected so great that there is no advantage in moving both inner cylinders with respect to the corresponding outer cylinders. The gears 47 and 43 by which the cylin ders 1a and lb are driven respectively remain in engagement regardless of the position of the cylinders.

A third arrangement for engaging and disengaging the two pairs of cylinder is illustrated in FIGS. ll, 12 and 13 which show an embodiment of the invention in side elevation, fragmentary front elevational section and sectional plan view respectively.

The two pairs of cylinders are respectively mounted on a stationary portion 49 and on a movable portion 5% of the press frame. As best seen from FIG. 12, the movable frame portion 50 is horizontally slidable on the stationary frame portion 49 over a distance corresponding to the gap 8 desired during relief printing operations. A handwheel 51 actuates the movement of the frame portions 4-9 and 50 relative to each other. It is mounted on the frame portion 54 by means of a rotatable shaft 52 which carries two bevel gears 53 in engagement with corresponding bevel gears 54 each fixedly fastened to a screw spindle 55. The spindles 55 are freely rotatable in a bracket 56 which is secured to the frame part 59, and threadedly engage a bracket 57 which is mounted on the stationary frame part 49. Upon rotation of the handwheel 5'1, the two pairs of cylinders are thus moved toward and away from a position of peripheral abutting engagement of the inner cylinders 2a and 2b. Since the movable frame portion 50 slides on a fiat bed of the stationary frame portion 49, the cylinders 1a and 2b move in rectilinear paths. FIG. 11 also shows some of the clustered rollers of the inking and damping systems 9a and 9b which of necessity move with the corresponding cylinders. The adjusted position of the frame portions '49, Si is secured by fastening screws 5? and 59.

Means for interchangeably securing various facings to the cylindrical surfaces of the cylinders 1a, 1b, 2a, and 2b are illustrated in FIGS. 14 to 21. It is emphasized that the facings described and the means for mounting them on a cylinder are not limited to use with any one specific cylinder in the printing unit of the invention, but that such facings and mounting means may be employed an any one of the cylinders as conditions may warrant.

FIG. 14, as an example, illustrates the outer cylinder 1a in axial. section, and a sectional front elevation on the line XV-XV of FIG. 14 is shown in FIG. 15. The cylinder has a solid body 60 which may be of steel or cast iron as is conventional in this art. The cylinder body is recessed to receive face plates -52 and a peripheral abutment ring 63 which circles the center portion of the cylinder body 61. Stereotype printing plates 61 are clamped between the face plates 62 and the ring 63 by means of clamping screws 64 which threadedly engage the face plates 62 and are rotatably mounted in recesses formed in radial faces of the cylinder body 60 and of oppositely arranged annular flanges 65 which are fastened to the front faces of the cylinder body 6%. The arrangement shown serves as a plate cylinder in the press of the invention when the latter is to be employed for relief printing.

The same cylinder is partly shown in FIG. 16 when arranged to receive image carriers of relatively small radial thickness such as etched plates for both relief and offset printing, the term offset printing being employed to designate both dry and wet offset, the latter being more commonly referred to as offset or offset lithographing printing.

When employed to carry a thin image carrier, the cylinder is provided with a layer of packing 66 to which the etched plates 67 are secured by means of adhesive. The thickness of the packing 66 is selected to provide the desired overall dimensions of the image surface.

Similarly, the cylinder may carry rubber printing plates 69 as shown in FIG. 17. The plates 69 are adhesively mounted on a thin metal sheet 70 which is mounted over packing '68 by means of one of the tensioning devices which will be described presently in more detail.

FIG. 18 illustrates a cylinder equipped for offset printing. The offset plate 7'2 of thin sheet metal is backed by packing '71. The packing is mounted between the face plates and the central abutment ring on the cylinder body in the manner described above in connection with the stereotype plates of FIG. 14.

The device for clamping a thin metal sheet to the cylinder surface is illustrated in FIGS. 19 and 20 which show sections through the cylinder of FIG. 18 on the line XIXXIX, FIG. 20 illustrating a detail of FIG. 19 on an enlarged scale. The same tensioning device may be employed to secure the plate carrying metal sheet 79 of FIG. 17.

As seen best in FIG. 20, a cylindrical tensioning rod 73 is rotatably inserted in a closely matching peripherally open recess in the cylinder body. A portion of the rod 73 (not shown) axially projects from the cylinder body so as to permit the rod to be rotated by a hand tool. The rod is arrested in the tensioning position in the same manner as shown below in connection with the tensioning device illustrated in FIG. 21.

One axial edge portion 74 of the offset plate 72 is clamped under the packing 71. The rod 73 has an axial slot 75 in which the other axial edge portion of the offset plate is received and in which it is held fast by means of a clamping block 76 and a fixing screw 77. Rotation of the rod 73 in the direction of the arrow causes the plate 72 closely to hug the cylindrical outer face of the packing 71.

FIG. 21 which shows a portion of an inner cylinder in side elevation, partly in section, illustrates means for securing a rubber offset blanket to the surface of a cylinder. A sheet metal reinforcing strip 79 is folded over an axial edge portion of the blanket 78 and is fastened to the blanket by pressure. The reinforced edge assembly is connected to a blanket tightening device by insertion in the slot 80 of a cylindrical tensioning rod 81 similar to the rod 73 shown in FIGS. 19 and 20.

The cylinder of FIG. 21 is equipped with two substantially identical blanket tightening devices each of which grips one axial edge portion of the offset blanket 78. Each device has a rod 81 carrying a worm wheel 82 which is engaged by a worm $3 the shaft of which carries a hexagonal head 84 adapted to be engaged by a mating Wrench for tensioning the blanket 78. The worm 83 is journaled in a split block 85 the two portions of which can be tightened by means of two screws 86 to clamp the worm 83 fast and to secure the tension in the blanket 7 8.

Since damping of an outer cylinder is not required when the printing unit of the invention is employed for relief printing, I prefer to equip a rotary press of the type described with a disengageable damping unit of which the apparatus shown in FIG. 22 is a preferred embodiment.

Three rollers 9, 9", and 9" are in sequential peripheral engagement to transmit damping liquid from a fountain (not shown) to the outer cylinder 1a. The rollers 9 and 9 are mounted in retractable bearings 87 which are axially movably mounted in the machine frame. The roller 9 is equipped with an axially movable gear shown in its inoperative position 88 in fully drawn lines. The gear can be shifted to its operative position 88' indicated in broken lines by a handle 89 provided with an arresting device 90 to prevent accidental shifting of the gear 8 8. Rotary movement is transmitted in the operative condition of the device from the gear 47 of the cylinder 1a to the gear of the roller 9' in the position 88, and therefrom to the gear 91 of the roller 9".

When the printing unit is to be employed for relief printing, the gear of the roller 9 is shifted into the in operative position 88, the corresponding bearing 37 is pulled outward, and the roller 9 is removed. No motion is transmitted from the cylinder 1a to the gear train of the damping mechanism. If desired, the roller 9" which is in direct contact with the damping liquid fountain may also be removed.

Shifting from offset printing to relief printing thus involves only very few simple operations with the printing press of my invention. The inner cylinders are moved away from each other by adjusting the positions of their bearings. The rubber blankets on the inner cylinders are replaced by a hard facing so that the inner cylinders can serve as impression cylinders, and a suitable set of printing plates is installed. The damping system is put into inactive condition. To return from relief to offset printing, the operations enumerated above are reversed.

Various modifications are contemplated and may obviously be resorted to by those skilled in the art without departing from the spirit and scope of the invention as hereinafter defined by the appended claims, as only preferred embodiments thereof have been disclosed.

I claim:

1. A rotary printing press for selective relief and offset printing, comprising, in combination, a support; a first and a second pair of cylinders, each pair consisting of an outer and an inner cylinder mounted on said support for rotation about parallel axes while in peripheral abutting engagement; means on said outer cylinders for mounting printing plates on the cylindrical surfaces thereof; means on said inner cylinders for alternatively mounting offset blankets and relief impression facings on the cylindrical surfaces thereof; and means for moving said inner cylinders toward a position in which the inner cylinders are parallel and in peripheral abutting engagemerit during offset printing and for moving said inner cylinders apart from their abutting engagement during relief printing.

2. A rotary printing press as set forth in claim 1, including a damping system releasably mounted on said support for transferring moisture to one of said cylinders.

3. The rotary printing press of claim 1, further comprising guide means for guiding a paper Web during relief printing in an S-shaped path first between the cylinders of said first pair and then between the cylinders of said second pair.

4. The rotary printing press of claim 1, comprising a plurality of units of said first and second pairs of cylinders.

References Cited in the file of this patent UNITED STATES PATENTS 859,587 Sherwood l July 9, 1907 1,018,151 Asmussen Feb. 20, 1912 1,178,907 Firm Apr. 11, 1916 1,459,312 Fritchard June 13, 1923 1,590,742 Goulding June 29, 1926 2,055,319 Smith Sept. 22, 1936 

1. A ROTARY PRINTING PRESS FOR SELECTIVE RELIEF AND OFFSET PRINTING, COMPRISING, IN COMBINATION, A SUPPORT; A FIRST AND A SECOND PAIR OF CYLINDERS, EACH PAIR CONSISTING OF AN OUTER AND AN INNER CYLINDER MOUNTED ON SAID SUPPORT FOR ROTATION ABOUT PARALLEL AXES WHILE IN PERIPHERAL ABUTTING ENGAGEMENT; MEANS ON SAID OUTER CYLINDERS FOR MOUNTING PRINTING PLATES ON THE CYLINDRICAL SURFACES THEREOF; MEANS ON SAID INNER CYLINDERS FOR ALTERNATIVELY MOUNTING OFFSET BLANKETS AND RELIEF IMPRESSION FACINGS ON THE CYLINDRICAL SURFACES THEREOF; AND MEANS FOR MOVING SAID INNER CYLINDERS TOWARD A POSITION IN WHICH THE INNER CYLINDERS ARE PARALLEL AND IN PERIPHERAL ABUTTING ENGAGEMENT DURING OFFSET PRINTING AND FOR MOVING SAID INNER CYLINDERS APART FROM THEIR ABUTTING ENGAGEMENT DURING RELIEF PRINTING. 